In recent years, polymer nanocomposites, which are composed of polymer matrices and nano-size fillers, attracted extensive research interests around the world. It has been found that these new kinds of materials have many advantages over the traditional ones such as increased strength without weakening other mechanical properties, decreased gas permeability, improved heat resistance, and enhanced electrical conductivity. Special interest has been focused on block copolymer/nanofiller systems, because in the general polymers/nanofillers system, until now, it is almost impossible to array nanofillers in the polymer matrices regularly, while in the block copolymers/nanofillers system, ordering of the nanofillers and thus creating highly organized hybrid materials are possible. The molecular chains of block copolymers have different segments that can self-assemble to form phase-separated microdomains. If one can make the fillers compatible with one of the phases in the block copolymer, it is possible that the fillers can segregate into the microdomains formed by this phase only and thus, the ordering of the fillers can be achieved by the self-assembling of the block copolymers. Such spatially regular materials could potentially be used in separation processes, catalysts, and photonic devices.
Although there have been some investigations into the properties of thin films of diblock copolymer/nanofiller systems, which have alternating regions of polymer-rich and particle-rich domains, systematic experimental studies to determine the factors governing the bulk morphology of copolymer/filler composites have not been undertaken yet as mentioned by Thompson et al. (R B Thompson, V V Ginzburg, M W Matsen, A C Balazs, Macromolecules 2002, 35, 1060). Most of the investigations are concentrated on the effects of the microdomains on the ordering of the fillers. Efforts to understand the effects of nanofillers on the phase-separation of the copolymers have not been reported.